A pelvic clamp of the type mentioned at the outset is disclosed, for example, in CH-A5-680561, has long been on the market and has proved its worth. For example, the procedure using it is described in the journal “Operative Orthopädie und Traumatologie [Surgical orthopaedics and traumatology]”, 2004, no. 2, pages 192-198. Although the present invention is not limited thereto it should be mentioned that a rail having a square profile was used as a rail-like straight guide in the case of the known pelvic clamp frequently referred to in the technical literature as “C-clamp”. The square profile ensures good guidance and is fairly torsionally rigid, and it is for this reason that it is also preferred for the present invention. However, it would of course also be possible within the scope of the invention, for example, to fix the position of two round profile rods parallel to one another in a frame.
During the use of the known pelvic clamp, certain problems have arisen which would permit a further improvement. In order to carry out a fixing of the position after driving the tip on the clamp nail in the correct position into the ilium, the two arms are moved relative to one another along the straight guide (i.e. in actual fact, it would also be sufficient to connect one arm firmly to the straight guide and to move only the other arm) whereupon the threaded spindles carrying the tips are screwed against the patient's pelvis until the rail bends. However, this means that canting occurs between rail and arms, which may be extremely disadvantageous on loosening.